Magneto-rheological elastomeric fluid control armature assembly

ABSTRACT

A solenoid fluid control valve having a valve body containing a solenoid coil, a fluid channel, and a seat, each coaxially disposed about a central longitudinal axis of the body, and a one-piece armature of MRE material. The armature is disposed within the fluid channel and magnetically actuable to seal against the seat, with operation of the solenoid coil actuating the armature with respect to the seat to alter the closure state of a fluid port. Also, a fluid check valve having a first valve body part defining a seat, a fluid port, and a first portion of a fluid chamber, with the seat including a permanent magnet element disposed adjacent the fluid port proximate the fluid chamber. A one-piece armature of MRE material is disposed across the fluid port and magnetically sealable against the magnet element. The armature and magnet element are configured to create a preselected magnetization offset pressure portion of a valve cracking pressure.

FIELD

The present disclosure is directed to fluid control valves and, moreparticularly, to magnetically actuated fluid control valves andself-actuating fluid check valves.

BACKGROUND

Direct-acting, magnetically-actuated fluid control valves are used in avariety of applications within industry. Typically, such valves includea solenoid coil and a metallic armature body manufactured from aferromagnetic alloy. The metallic armature body is capped with anelastomeric sealing member which seals against a seat within the body ofthe valve to control the flow of fluid through the valve. A spring maybias the metallic armature body into a normally open or normally closedposition, whereupon powering the solenoid coil of the valve magneticallyactuates the metallic armature body against the bias (either toward theseat to seal a fluid port or away from the seat to unseal a fluid port,respectively) to alter the closure state of the valve. The elastomericsealing member may provide for both fluid sealing and impact absorptionduring operation of the valve.

Self-actuating fluid check valves are also commonly used withinindustry, household fixtures, and consumer products. Typically, suchvalves include a resilient sealing member, such as an elastomeric ballor disc, which may be biased against a seat in the valve body bygravity, by preloading via a spring, or by the intrinsic resilience ofthe sealing member (such as in an umbrella valve). The flow of fluidfrom an upstream side of the valve displaces the sealing member from theseat, allowing fluid to flow past the sealing member and to a downstreamfluid port in the valve. The biasing of the sealing member, as well asany flow of fluid into the downstream port the valve (a reversed flow),drives the sealing member toward seat and, upon sealing engagement,serves to prevent fluid from flowing past the sealing member to anupstream fluid port of the valve. Fluid check valves may also desirablyhave a minimum “cracking pressure,” defined as the minimum upstreampressure required to open the valve and start fluid flow through thevalve. That cracking pressure is conventionally varied by altering thepreloading displacement or spring constant of a biasing spring, byaltering the preloading displacement or modulus of elasticity of thesealing member material, or by related means.

SUMMARY

The applicant has determined that such fluid control valves may beadvantageously enhanced, whether through simplified construction orgreater flexibility in material selection and other design constraints,by manufacturing the sealing armature from a magneto-rheologicalelastomer material or “MRE.” Such materials comprise an elastomer, suchas a natural or synthetic rubber compound, and a particulateferromagnetic material, such as a ferrite, prepared as an essentiallyhomogeneous suspension. The MRE material is subsequently molded, formed,or shaped into an armature body shape by various mechanical and chemicalprocesses depending upon whether the elastomer matrix is a rubber(vulcanization), a thermoset (thermal or chemical curing), athermoplastic (cooling below an elevated melting temperature), etc. Suchmaterials, when formed into a magneto-rheological elastomeric armature,may simplify actuator and/or sealing armature construction, allow forsubstantial reductions in valve component size, and enable more compactvalve body designs.

An MRE sealing armature may be incorporated into a solenoid fluidcontrol valve to provide a one-piece, magnetically-actuable armaturewhich effectively seals a fluid port. Even more advantageously, an MREsealing armature may be incorporated into a self-actuating fluid checkvalve having a permanent magnet element in order to abolish dependenciesupon valve orientation, to eliminate the need for a biasing spring,and/or to endow a particular valve design with greater flexibility inconfigured cracking pressure by altering the preload or apparent pliancyof a sealing armature without necessarily altering a springcharacteristic or switching to a less pliant armature material. The MREsealing armatures and disclosed valve designs consequently providesignificant advantages such as simplified construction and greaterflexibility in design and material selection over conventionaldirect-acting, magnetically-actuated or self-actuating fluid controlvalve designs.

In a first aspect, the disclosure pertains to a magnetically-actuated,solenoid fluid control valve. The valve has a valve body containing asolenoid coil, a fluid channel, and a seat, each coaxially disposedabout a central longitudinal axis of the valve body, and a one-piecearmature of MRE material. The one-piece armature is disposed within thefluid channel and magnetically actuable to bring a sealing end intosealing engagement with the seat, and the fluid channel has a first endincluding a first fluid port in fluid communication with the seat,whereby operation of the solenoid coil actuates the one-piece armaturewith respect to the seat to alter the closure state the first fluidport. It is noted that magnetic actuation may include actuation of theone-piece armature while powering the solenoid coil to create andsustain a magnetic field, as well as actuation of the one-piece armaturewhile depowering the solenoid coil to collapse the magnetic field.

In a second aspect, the disclosure pertains to a self-actuating fluidcheck valve. The valve has a first valve body part defining a seat, afluid port, and a first portion of a fluid chamber, with the seatincluding a permanent magnet element disposed adjacent the fluid portproximate the fluid chamber. A one-piece armature of MRE material isdisposed across the fluid port and magnetically sealable against thepermanent magnet element of the seat. The one-piece armature and thepermanent magnet element are configured to create a preselectedmagnetization offset pressure portion of a valve cracking pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional profile view of a normally closed solenoid fluidcontrol valve in a closed position.

FIG. 2 is a sectional profile view of the normally closed solenoid fluidcontrol valve of FIG. 1 in an open position.

FIG. 3 is a sectional end view of a solenoid fluid control valve showingan optional guide projection 118 in the armature and a complementaryguide channel 149 in the valve body, an optional guide channel 119 inthe armature and a complementary guide projection 148 in the valve body,an optional internal passage in the armature, and optional surfacechannel in the armature.

FIG. 4 is a sectional profile view of a normally open solenoid fluidcontrol valve in an open position.

FIG. 5 is a sectional profile view of the normally open solenoid fluidcontrol valve of FIG. 4 in a closed position.

FIG. 6 is a sectional perspective view of a self-actuating fluid checkvalve incorporating an MRE sealing armature in a closed position.

FIG. 7 is a sectional perspective view of the self-actuating fluid checkvalve of FIG. 6 in an open position.

FIG. 8 is a sectional perspective view of a self-actuating fluid checkvalve incorporating an MRE umbrella-type sealing armature.

FIG. 9 is a sectional profile view of the self-actuating fluid checkvalve of FIG. 8, further including an exemplary second valve body partfor forming an enclosed fluid chamber and downstream fluid port.

DETAILED DESCRIPTION

A first aspect of the disclosure is a magnetically-actuated, solenoidfluid control valve 100. With initial reference to FIG. 1, the solenoidfluid control valve 100 incorporates a one-piece armature 110manufactured from a magneto-rheological elastomer or MRE. The MREgenerally comprises an elastomer matrix containing a dispersedparticulate ferromagnetic filler. In one exemplary implementation, theelastomer is a vulcanized natural rubber, and the ferromagnetic filleris a particulate strontium ferrite present in a range about 70% to about84% by weight. In another exemplary implementation the elastomer is asynthetic rubber or polymer such as EPDM (ethylene-propylene-dienemonomer) or SEBS (styrene-ethylene-butylene-styrene), and theferromagnetic filler is a particulate barium ferrite present in a rangeabout 70% to about 84% by weight. The material preferably has a Shorehardness of about 55 to about 85 on the Shore A scale. Those of skill inthe art will appreciate that the Shore hardness of the material ofarmature 110 will tend to be greater than that of the elastomer itselfdue to the amount and form of the ferromagnetic filler incorporated intothe elastomer matrix, and that varying combinations of particularelastomers and ferromagnetic fillers may be used to manufacture thearmature 110. The one-piece armature is preferably an essentiallyhomogeneous mixture of these materials, yet may be coated with adifferent polymer than that of the elastomer matrix, such aspolytetrafluoroethylene, in order to provide increased chemicalresistance and/or increased resistance to fouling.

The solenoid fluid control valve 100 more generally comprises a valvebody 120 containing a solenoid coil 130, a fluid channel 140, and a seat150 each coaxially disposed about a central longitudinal axis “L.” Afirst end of the fluid channel 140 includes a first fluid port 160 influid communication with the seat 150, with the seat being configuredfor sealing engagement with a sealing end 112 of the one-piece armature110. In operation, a force may bias the one-piece armature 110 withrespect to the seat 150, with the sealing end 112 entering into sealingengagement with the seat 150 to prevent fluid flow through the firstfluid port 160 or withdrawing from sealing engagement with the seat 150to allow fluid flow through the first fluid port 160. Another portion ofthe fluid channel 140, such as the second end of the fluid channel,includes a second fluid port 170 to permit flow within the fluid channel140 and through the valve 100. It will be appreciated that the secondfluid port 170 may alternately be disposed in the sidewall of the fluidchannel 140 or even in a non-coaxially disposed segment or branch of thefluid channel 140, rather than the axially aligned location illustratedin the figures.

In a first embodiment, shown in FIGS. 1 and 2, the fluid control valve100 is a normally closed fluid control valve, and includes a spring 180coaxially disposed about the central longitudinal axis L within thefluid channel 140 opposite the seat 150. This spring 180 may matinglyengage with a profiled spring contact 114 on the end of the one-piecearmature 110 opposite the sealing end 112. For example, the profiledspring contact 114 may include a peripheral land 115 surrounding aprojecting nub 116, with the nub 116 preferably including a chamferedperipheral surface 117 to enhance pulling force into the solenoid coil130. The one-piece armature 110 and fluid channel 140 are preferablygenerally cylindrical, but it will be appreciated that the theseelements may have other cross-sectional profiles as well, includinggenerally ellipsoidal, rectangular, or square profiles, in order tomaintain the one-piece armature 110 in a preset orientation. As shown inFIG. 3, the one-piece armature 110 and fluid channel 140 may alternatelyor additionally include complementary guide elements such as projections118, 148 and channels 119, 149 in order to maintain the one-piecearmature 110 in a preset orientation. The one-piece armature 110 maygenerally have the described cross sections while also incorporatinginternal passages 111 or surface channels 113 for the delivery of fluidto other fluid ports, such as in some three-way solenoid fluid controlvalve designs. Operation of the solenoid coil 130 actuates the one-piecearmature 110 with respect to the seat 150 to overcome the spring'sclosing bias and seal the fluid port 160 against fluid flow.

In a second embodiment, shown in FIGS. 4 and 5, the fluid control valve100 is a normally open fluid control valve, and includes a spring 180coaxially disposed about the central longitudinal axis L within thefluid channel 140 and around the seat 150. This spring 180 may matinglyengage with a profiled spring contact 114 on the sealing end 112. Forexample, the profiled spring contact may include a peripheral land 115surrounding a projecting sealing nub 116, with the sealing nub 116preferably including a chamfered peripheral surface 117 to enhancepulling force into the solenoid coil 130, as well as to seal against acomplementary chamfered peripheral surface in a seat recess 152 formedin seat 150. As in the first embodiment, the one-piece armature 110 andfluid channel 140 are preferably generally cylindrical, but may haveother cross sectional profiles as well, and may alternately oradditionally include complementary guide elements such as projections118, 148 and guide channels 119, 149. The one-piece armature 110 mayagain generally have the described cross sections while incorporatinginternal passages 111 or surface channels 113 for the delivery of fluidto other ports. Operation of the solenoid coil 130 actuates theone-piece armature 110 with respect to the seat 150 to overcome thespring's opening bias and seal the fluid port 160 to prohibit fluidflow.

Those of skill in the art will appreciate that the spring 180,particularly in a normally open fluid control valve, is an optionalcomponent that may be provided to ensure the desired bias, however insome normally open fluid control valves fluid pressure may providesufficient bias towards an open state. Similarly, in some fluid controlvalves the solenoid coil 130 may be normally powered in order to holdthe valve in a normally closed state, however this form of valve willconsume more energy (which must be dissipated as heat) than normallyclosed valves incorporating a biasing spring. In yet other fluid controlvalves, a second solenoid coil could be disposed within the valve bodyto create a low-power/high-power coil pair which may be used to shuttlethe one-piece armature 110 between open and closed positions, with onemember of the pair ensuring the desired opening or closing bias, and theother member of the pair being operated to overcome the second solenoidcoil's opening or closing bias.

A second aspect of the disclosure is a self-actuating fluid check valve200. With initial reference to FIG. 6, the fluid check valve 200incorporates a one-piece armature 210 manufactured from amagneto-rheological elastomer or MRE. As in the first embodiment, theMRE generally comprises an elastomer matrix containing a dispersedparticulate ferromagnetic filler. In one exemplary implementation, thepolymer is a vulcanized natural rubber, and the ferromagnetic filler isa particulate strontium ferrite present in a range about 70% to about84% by weight. In another exemplary implementation the elastomer is asynthetic rubber or polymer such as a PUR (polyurethane ether orpolyurethane ester) and the ferromagnetic filler is a particulate bariumferrite present in a range about 70% to about 84% by weight. Thematerial preferably has a Shore hardness of about 55 to about 85 on theShore A scale. The one-piece armature 210 is preferably an essentiallyhomogeneous mixture of these materials, but may be coated with othermaterials, such as a mechanically compatible fluoropolymer, in order toprovide increased chemical resistance. The one-piece armature 210 may beconfigured as a disk sealing member, an umbrella sealing member, a ballsealing member, a hinged flap sealing member, etc.

The fluid check valve 200 generally comprises a first valve body part220 defining a seat 250, a fluid port 260, and a first portion of afluid chamber 240. The seat 250 includes a permanent magnet element 252disposed adjacent to, and preferably around, the fluid port 260proximate the first portion of the fluid chamber 240. In varyingembodiments, the permanent magnet element 252 may comprise an annulus ofpermanently magnetized material disposed coaxially about the fluid port260. Another portion of the fluid chamber 240, e.g., another portion ofthe first valve body part 220, a portion of a second valve body part 230defining a second portion of the fluid chamber 240 (as shown in FIG. 9),or a combination of the parts 220 and 230, defines a downstream fluidport 270 to permit flow through the fluid chamber 240 and the valve 200.It will be appreciated that the downstream fluid port 270 may be anyopening to a downstream fluid path connected to the fluid chamber 240,although preferably the downstream fluid port 270 is configured so as toretain the one-piece armature 210 within the fluid chamber 240 of thevalve 200. As discussed in further detail below, the one-piece armature210 and the permanent magnet element 252 are configured to create apreselected magnetization offset pressure portion of a valve crackingpressure.

In a first embodiment, shown in FIGS. 6 and 7, the fluid check valve 200is a disk valve, with one-piece armature 210 being configured as a diskand held in proximity to the fluid port 260 between the first and secondvalve body parts 220, 230. The permanent magnet element 252 is anannulus of permanently magnetized material disposed coaxially about thefluid port 260, with the magnetic properties of the annulus and diskserving to center and reseat the one-piece armature 210 against the seat250 in the event of a cessation of flow, or reverse flow, through thedownstream fluid port 270. In alternate embodiments, guide elements suchas projections from the valve body parts 220 and/or 230 into the fluidchamber 240 and, optionally, complementary channels or apertures in theone-piece armature 210 may be used to retain the armature in positionacross the fluid port 260. Those of skill in the art will appreciatethat the disk and/or annulus need not be truly circular as illustratedin the figures, but may be generally ellipsoidal or generally polygonalas well. Those of skill in the art will also appreciate that in otheralternate embodiments, the one-piece armature 210 may be configured as aball and held in proximity to the fluid port 260 between the first andsecond valve body parts 220, 230, with first valve body part 220 beingformed into a funnel-like shape to further direct the one-piece armature210 to seat within the annulus of permanent magnet element 252.

In a second embodiment, shown in FIG. 8, the fluid check valve 200 is anumbrella-type valve, with one-piece armature 210 being configured as anumbrella element and secured across fluid port 260 through engagement ofthe fluid port with the umbrella stem. The permanent magnet element 252is an annulus of permanently magnetized material disposed coaxiallyabout the fluid port 260, with the umbrella skirt of the one-piecearmature 210 reseating against the seat 250 in proximity to thepermanent magnet element 252 in the event of a cessation of flow, orreverse flow, through the downstream fluid port 270. Those of skill inthe art will appreciate that the umbrella stem of an umbrella element issimilar to the fixed portion of a flap sealing member having a livinghinge. The one-piece armature 210 may accordingly be configured in otherembodiments to have a fixed portion secured to the first valve body part220 radially beyond the permanent magnet element 252, and a flap portionextending across the seat 250, permanent magnet element 252, and fluidport 260 so as to seal the fluid port 260 to prevent fluid flow.

In general, the attractive force between an annulus of magnetic materialand a generally planer one-piece armature 210 (such as the face of adisk sealing member, the annular contact portion of an umbrella sealingmember, or the flap portion of a flap sealing member) can be estimatedby:

$\begin{matrix}{F = {\frac{B_{m}^{2}*A*L}{\mu}*P_{f}}} & (1)\end{matrix}$

where F is the attractive force, B_(m) is the maximum magnetic inductionof the particulate ferromagnetic filler material, P_(f) is the weightpercent of the particulate ferromagnetic filler material in the MRE, Ais the area of surface contact between the one-piece armature 210 andthe annulus of magnetic material (permanent magnet element 252), L isthe average thickness of the one-piece armature 210 over the area ofsurface contact, and μ is the permeability coefficient of the mediumbetween the one-piece armature 210 and the permanent magnet element 252,if known (with air being ˜1.000000). Dividing this force by the area ofsurface contact yields a magnetization offset pressure, which may betreated as a valve cracking pressure, P_(mo), or in cases such asumbrella valves where resiliency of the valve material furthercontributes to valve cracking pressure, a magnetization offset pressureportion of the valve cracking pressure.

Example 1

Several one-piece armatures 210 were manufactured in the form of discsealing members from a sulfur-cured EPDM polymer containing varyingamounts of STARBOND HM410, a strontium ferrite filler supplied byHoosier Magnetics, Inc. of Ogdensburg, N.Y. B_(m) and μ for the fillerwere 2.2 kiloGauss and 1, respectively. Six different disc exemplarswere created from sheets of MRE material having a thickness (L) ofeither 0.075 inches or 0.040 inches and one of three levels ofparticulate ferromagnetic filler material: 69.6 wt. percent, 79.3 wt.percent, or 84.7 wt. percent. The area of contact (A) between an annularpermanent magnet (circular, approximately 2 inch outside diameter and9/16 inch inside diameter) and an armature disc (circular, approximately2 inch diameter) was 2.04 inches² so as to yield the estimated crackingpressures shown in Table 1.

TABLE 1 Estimated Check Valve Cracking Pressure Filler Disc Thickness(L) material (P_(f)) Est. Force Est. Cracking Exemplar (inches) (wt.percent) (lbs.) Pressure (psi) A 0.075 69.6 0.515 0.249 B 0.075 79.30.587 0.283 C 0.075 84.7 0.627 0.303 D 0.040 69.6 0.275 0.133 E 0.04079.3 0.313 0.151 F* 0.040 84.7 0.335 0.161Disc exemplar F was not successfully created and tested. Test sheetsmolded at this thickness and filler content could not be demoldedwithout tearing due to adhesion to the mold and insufficient tensilestrength.

The force required to separate the disc exemplars from the permanentmagnet was measured using an Instron 4411 tensile machine equipped witha 5 KiloNewton load cell. Each disc exemplar was connected in turn tothe grips in the crosshead of machine using monofilament line, and thecrosshead was operated at a rate of 5 inches per minute. The peak forcegenerated during displacement of the crosshead was identified anddivided by A to calculate the experimental cracking pressure of theone-piece armatures 210, reported in Table 2. The test was repeatedthree times upon each exemplar, and the values averaged for reporting.

TABLE 2 Experimental Check Valve Cracking Pressure (Instron 4411testing) Measured Measured Cracking Error in Estimate of Force (lbs.)Pressure (psi) Cracking Pressure Disc Exemplar (lbs.) (psi) (Δ vs.Measured, %) A 0.510 0.246 −1 B 0.456 0.220 −29 C 0.537 0.259 −17 D0.242 0.117 −14 E 0.268 0.130 −17 F N/A N/A N/AThe average error in the estimate of cracking pressure versus theexperimental results was −15%, suggesting some element of systematicerror in the experimental measurement technique and/or systematic errorin the model of equation (1) due to an omitted term. However, a generaltrend in cracking pressure as a function of armature thickness andcomposition will be apparent to those of ordinary skill in the art.

The various aspects and implementations described above are intended tobe illustrative in nature, and are not intended to limit the scope ofthe invention. Any limitations to the invention will appear in theclaims as allowed.

What is claimed is:
 1. A magnetically-actuated, solenoid fluid controlvalve comprising: a valve body containing a solenoid coil, a fluidchannel, and a seat, each coaxially disposed about a centrallongitudinal axis of the valve body; and a one-piece armature comprisingan elastomer matrix containing a dispersed particulate ferromagneticfiller, the one-piece armature being disposed within the fluid channeland magnetically actuable to bring a sealing end into sealing engagementwith the seat; the fluid channel having a first end including a firstfluid port in fluid communication with the seat, whereby operation ofthe solenoid coil actuates the one-piece armature with respect to theseat to alter the closure state the first fluid port.
 2. Themagnetically actuated, solenoid fluid control valve of claim 1, whereinthe elastomer matrix is a synthetic rubber, and the ferromagnetic filleris a particulate strontium ferrite present in a range about 70% to about84% by weight.
 3. The magnetically actuated, solenoid fluid controlvalve of claim 1, wherein the combined elastomer matrix and dispersedparticulate filler have a Shore hardness of about 55 to about 85 on theShore A scale.
 4. The magnetically actuated, solenoid fluid controlvalve of claim 1, wherein the valve is a normally closed valve, thevalve further comprising: a spring coaxially disposed about the centrallongitudinal axis and within the fluid channel opposite the seat,wherein the spring biases the sealing end against the seat to seal thefirst fluid port.
 5. The magnetically actuated, solenoid fluid controlvalve of claim 4 further comprising: a profiled spring contact disposedon the end of one-piece armature opposite the sealing end, the profiledspring contact including a peripheral land surrounding a projecting nub.6. The magnetically actuated, solenoid fluid control valve of claim 5,wherein the projecting nub includes a chamfered peripheral surface. 7.The magnetically actuated, solenoid fluid control valve of claim 1,wherein the valve is a normally open valve, the valve furthercomprising: a spring coaxially disposed about the central longitudinalaxis and within the fluid channel around the seat, wherein the springbiases the sealing end away from the seat to open the first fluid port.8. The magnetically actuated solenoid fluid control valve of claim 7further comprising: a profiled spring contact disposed on the sealingend of one-piece armature, the profiled spring contact including aperipheral land surrounding a projecting nub.
 9. The magneticallyactuated solenoid fluid control valve of claim 8, wherein the projectingnub includes a chamfered peripheral surface.
 10. Themagnetically-actuated, solenoid fluid control valve of claim 1, whereinthe one-piece armature consists essentially of a homogeneous suspensionof the ferromagnetic filler within the elastomer matrix.
 11. Themagnetically-actuated, solenoid fluid control valve of claim 10, whereinthe one-piece armature is coated with a different polymer than that ofthe elastomer of the elastomer matrix.
 12. The magnetically-actuated,solenoid fluid control valve of claim 1, wherein the one-piece armatureincludes a guide element for maintaining the armature in a presetorientation, and the valve body includes a complementary guide elementengaging the armature guide element.
 13. The magnetically-actuated,solenoid fluid control valve of claim 1, wherein the one-piece armatureincorporates an internal passage or surface channel for the delivery offluid to another fluid port.
 14. A self-actuating fluid check valvecomprising: a first valve body part defining a seat, a fluid port, and afirst portion of a fluid chamber, the seat including a permanent magnetelement disposed adjacent the fluid port proximate the fluid chamber; asecond valve body part defining a second portion of the fluid chamber;and a one-piece armature comprising an elastomer matrix containing adispersed particulate ferromagnetic filler, the one-piece armature beingdisposed across the fluid port and magnetically sealable against thepermanent magnet element of the seat; the one-piece armature and thepermanent magnet element being configured to create a preselectedmagnetization offset pressure portion of a valve cracking pressure. 15.The self-actuating fluid check valve of claim 14, wherein the elastomermatrix is a synthetic rubber, and the ferromagnetic filler is aparticulate strontium ferrite present in a range about 70% to about 84%by weight.
 16. The self-actuating fluid check valve of claim 15, whereinthe combined elastomer matrix and dispersed particulate filler have aShore hardness of about 55 to about 85 on the Shore A scale.
 17. Theself-actuating fluid check valve of claim 14, wherein the permanentmagnet element is an annulus of permanently magnetized material disposedcoaxially about the fluid port.
 18. The self-actuating fluid check valveof claim 14, wherein the valve is a disk valve, and the one-piecearmature is configured as a disk.
 19. The self-actuating fluid checkvalve of claim 18, wherein at least one of the first and second bodyportions includes guide elements projecting into the fluid chamber, andthe one-piece armature includes complementary guide elements engagingthe projecting guide elements to retain the one-piece armature inposition across the fluid port
 20. The self-actuating fluid check valveof claim 14, wherein the valve is an umbrella valve, and the one-piecearmature is configured as an umbrella element having an umbrella stem,with the one-piece armature umbrella stem being secured across the fluidport through engagement of the fluid port with the umbrella stem.